Re: The TC in Pats.No.645576 & 649621

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Scott Fulks by way of Terry Fritz <twftesla-at-qwest-dot-net>" <darkthing-at-earthlink-dot-net>

Matt D. wrote:
> dimensions: Primary one Turn Diameter of 8ft (244 cm) , capacitor 0.04 uf,
> fr=230kHz, V(in)=50KV.
> This seems to be contradictory. Using the flat spiral formula
(NR)^2/(8R+11B)
> with N=1, R=48" and B=0.25", I get L= ~6 uH for the primary.
Back-calculating
> from fr=1/(2pi(LC)^0.5) with C=0.04 and fr=230kHz) I get L= ~12 uH.

I don't think there is a discrepancy here.  Reading the patent, Tesla says
that the primary inductance by itself was 8000 cm (8uH) and the entire
primary circuit had an inductance of 10,000 cm (10 uH).  The extra
inductance is probably due to the cables connecting the primary to the tank
cap, which in an apparatus of this size can be non-trivial.  At 0.04 uF
capacitance, 10 uH gives a frequency of 250 kHz, and Tesla says that "the
primary circuit vibrated generally according to adjustment, from 230,000 to
250,000 times per second".  Keep in mind that it is common to make the
primary longer than necessary and adjust the tap point to give the best
output.  So, it wouldn't surprise me if Tesla built a two turn primary but
tapped it at a little over 1 turn, thus describing it as a 1 turn primary
but drawing it with two.

>         The secondary is also a flat spiral, of 50 Turns #8 wire. (Tesla
> call this "thin wire") R=47" ,B=47", N=50--> Ls=14.68 mH, V(out)= ~2-4 MV.
> The Axes of the coils are horizontal. At this point, the equations that I
am
> familiar with no longer apply. (e.g., self capacitance, etc.) Can any of
the
> theoreticians, mathematicians, et. al. help with these calculations

Self capacitance of a loosely wound 50 turn secondary would be trivial, I
think.  At 15 mH or so inductance, you would need 27 pF to get a 250 kHz
resonance, and I think this pretty much has to all come from the topload.

Regards,
Scott Fulks (darkthing-at-earthlink-dot-net)